A number of Panasonic Lumix GH5 owners using Final Cut Pro X with LUT loading plug-ins have reported varying LUT interpretation results with 8-bit and 10-bit footage. The problem involves clamping or lowering the footage superwhites after LUTs have been applied.

High whites are well-preserved in GH5 V-Log 10-bit 4:2:2 footage with Leeming LUT One applied in Premiere Pro, before and after

So far the specific causes of this problem, and its permanent solution, have not been 100% identified, but it may be useful to share a list of the free and paid-for LUT plug-ins and related software that are currently available. If the cause resides in one or more specific LUT plug-ins, then it may be wise to try out others on the list below.

ScopeBox – professional scopes application for macOS computers, that allows feeding video from a range of DIT tools and Adobe video software as well as Final Cut Pro X into ScopeBox via ScopeLink. ScopeBox maker divergent media says that “the scopes found in most desktop editing applications leave a lot to be desired – they’re not accurate, they’re slow, and they’re not configurable”.

The crux of the problem and a workaround

Paul Leeming of Leeming LUT One describes the problem as follows. The LUTs from his unified, corrective LUT system are “designed to maximize dynamic range, fix skin tones, remove unwanted colour casts and provide an accurate Rec. 709 starting point for further creative colour grading”.

The Leeming LUT One system provides “the best possible settings to maximise dynamic range and image quality for that camera, while minimising noise and other unwanted artefacts”. Thus the system’s LUTs are “designed to work with the full float levels of the video clips as they come out of camera”.

“Some cameras stop at 100 IRE, but others such as Panasonic and Sony retain superwhite up to 109 IRE (usually), so my LUTs are designed around that limit, not the 100 IRE limit,” Mr Leeming says.

He offers one potential workaround, until LUT plug-ins are updated to support float space. “The easiest temporary solution is to adjust IRE for clips to fall within 0-100 IRE, then apply the LUT, as in theory the distribution of values in float space should be the same. That should avoid clipping”.

Mr Leeming notes that he designs Leeming LUT One in Premiere Pro which “handles superwhites with the LUT directly” and “no need to pull down exposure” and was “not aware that there were programs which didn’t pull down superwhites or lift superblacks”.

A more permanent solution

Roger Bolton of CoreMelt, developer of Chromatic and LUTx, has further insights into the problem and its solution:

A LUT is defined in the color ranges 0-1 in float with 1 being defined as the highest legal level (100 IRE). You can stretch the LUT out to handle the additional levels but that’s changing the look of the LUT if it was designed on legal levels. There’s not really a “correct” solution that I’m aware of, so how a LUT loader should handle this is something that needs flexibility.

As Chromatic is currently under development, Mr Bolton says that “we plan to allow a few different ways of dealing with the issue” and has asked users to send him their requests. He states that LUTx will be updated to handle superwhites and Chromatic will also handle them when released.

Update

CoreMelt has released Chromatic and its is available as a 14-day free trial or as a special launch offer for one week only, closing at Pacific Standard Time (PST) 7th August 2017. The special offer contains Chromatic and over 150 LUTs.